<script id="draw-shader-vs" type="x-shader/x-vertex">
precision mediump float;

attribute vec3 inPos;
attribute vec3 inNV;
attribute vec3 inCol;

varying vec3 vertPos;
varying vec3 vertNV;
varying vec3 vertCol;
varying vec4 clip_space_pos;
    
uniform mat4 u_projectionMat44;
uniform mat4 u_viewMat44;
uniform mat4 u_modelMat44;

void main()
{
    vec3 modelNV  = mat3( u_modelMat44 ) * normalize( inNV );
    vertNV        = mat3( u_viewMat44 ) * modelNV;
    vertCol       = inCol;
    vec4 modelPos = u_modelMat44 * vec4( inPos, 1.0 );
    vec4 viewPos  = u_viewMat44 * modelPos;
    vertPos       = viewPos.xyz / viewPos.w;
    gl_Position   = u_projectionMat44 * viewPos;
}
</script>

<script id="draw-shader-fs" type="x-shader/x-fragment">
precision mediump float;

varying vec3 vertPos;
varying vec3 vertNV;
varying vec3 vertCol;

struct Light {
    vec3  position;
    vec3  direction;
    float ambient;
    float diffuse;
    float specular;
    float shininess;
    vec3  attenuation;
    float cutOffAngle;
};
uniform Light u_light;

void main()
{
    vec3  color     = vertCol;
    vec3  lightCol  = u_light.ambient * color;
    vec3  normalV   = normalize( vertNV );
    vec3  lightV    = normalize( u_light.position - vertPos );
    float lightD    = length( u_light.position - vertPos );
    float cosL      = dot( normalize( u_light.direction ), -lightV );
    float inCone    = step( cos( u_light.cutOffAngle * 0.5 ), cosL );
    float att       = 1.0 / dot( vec3( 1.0, lightD, lightD*lightD ), u_light.attenuation );
    float NdotL     = max( 0.0, dot( normalV, lightV ) );
    lightCol       += NdotL * u_light.diffuse * color * inCone * att;
    vec3  eyeV      = normalize( -vertPos );
    vec3  halfV     = normalize( eyeV + lightV );
    float NdotH     = max( 0.0, dot( normalV, halfV ) );
    float kSpecular = ( u_light.shininess + 2.0 ) * pow( NdotH, u_light.shininess ) / ( 2.0 * 3.14159265 );
    lightCol       += kSpecular * u_light.specular * color * inCone * att;
    gl_FragColor    = vec4( lightCol.rgb, 1.0 );
}
</script>

<script id="light-cone-shader-vs" type="x-shader/x-vertex">
precision mediump float;
attribute vec2 inPos;
varying vec2 vertPos;
void main()
{
    vertPos.xy  = inPos.xy;
    gl_Position = vec4( inPos, 0.0, 1.0 );
}
</script>

<script id="light-cone-shader-fs" type="x-shader/x-fragment">
precision mediump float;

varying vec2 vertPos;

uniform sampler2D u_colorAttachment0;
uniform vec2  u_depthRange;
uniform vec2  u_vp;
uniform float u_fov;

struct Light {
    vec3  position;
    vec3  direction;
    float ambient;
    float diffuse;
    float specular;
    float shininess;
    vec3  attenuation;
    float cutOffAngle;
};
uniform Light u_light;

void main()
{
    vec4 texCol = texture2D( u_colorAttachment0, vertPos.st * 0.5 + 0.5 );
    
    vec3 vLightPos  = u_light.position;
    vec3 vLightDir  = normalize( u_light.direction );
    float tanFOV    = tan(u_fov*0.5);
    vec3  nearPos   = vec3( vertPos.x * u_vp.x/u_vp.y * tanFOV, vertPos.y * tanFOV, -1.0 );
    //vec2 texCoord = gl_FragCoord.xy / u_vp;
    //vec3 nearPos  = vec3( (texCoord.x-0.5) * u_vp.x/u_vp.y, texCoord.y-0.5, -u_depthRange.x );
    vec3 los        = normalize( nearPos );
    
    // ray definition
    vec3 O = vec3(0.0);
    vec3 D = los;

    // cone definition
    vec3  C     = vLightPos;
    vec3  V     = vLightDir;
    float cosTh = cos( u_light.cutOffAngle * 0.5 );
    
    // ray - cone intersection
    vec3  CO     = O - C;
    float DdotV  = dot( D, V );
    float COdotV = dot( CO, V );
    float a      = DdotV*DdotV - cosTh*cosTh;
    float b      = 2.0 * (DdotV*COdotV - dot( D, CO )*cosTh*cosTh);
    float c      = COdotV*COdotV - dot( CO, CO )*cosTh*cosTh;
    float det    = b*b - 4.0*a*c;
    
    // find intersection
    float isIsect = 0.0;
    vec3  isectP  = vec3(0.0);
    if ( det >= 0.0 )
    {
        vec3  P1 = O + (-b-sqrt(det))/(2.0*a) * D;
        vec3  P2 = O + (-b+sqrt(det))/(2.0*a) * D;
        float isect1 = step( 0.0, dot(normalize(P1-C), V) );
        float isect2 = step( 0.0, dot(normalize(P2-C), V) );
        if ( isect1 < 0.5 )
        {
            P1 = P2;
            isect1 = isect2;
        }
        if ( isect2 < 0.5 )
        {
            P2 = P1;
            isect2 = isect1;
        }
        isectP = ( P1.z > -u_depthRange.x || (P2.z < -u_depthRange.x && P1.z < P2.z ) ) ? P2 : P1;
        isIsect = mix( isect2, 1.0, isect1 ) * step( isectP.z, -u_depthRange.x );
    }
    
    float dist = length( isectP - vLightPos.xyz );
    float att  = 1.0 / dot( vec3( 1.0, dist, dist*dist ), u_light.attenuation );        
    
    
    gl_FragColor = vec4( mix( texCol.rgb, vec3(1.0, 1.0, 1.0), isIsect * att * 0.5 ), 1.0 );
}
</script>

<style>
html,body { margin: 0; overflow: hidden; }
#gui { position : absolute; top : 0; left : 0; font-size : large; }
#ref-link { position : absolute; bottom : 0; left : 0; font-size : large; }  
</style>

<body>
<div><form id="gui" name="inputs">
<table>
    <tr> <td> <font color=#40f040>ambient</font> </td> 
            <td> <input type="range" id="ambient" min="0" max="100" value="0"/></td> </tr>
    <tr> <td> <font color=#40f040>diffuse</font> </td> 
            <td> <input type="range" id="diffuse" min="0" max="100" value="0"/></td> </tr>
    <tr> <td> <font color=#40f040>specular</font> </td> 
            <td> <input type="range" id="specular" min="0" max="100" value="0"/></td> </tr>
    <tr> <td> <font color=#40f040>shininess</font> </td> 
            <td> <input type="range" id="shininess" min="1" max="100" value="0"/></td> </tr>
    <tr> <td> <font color=#40f040>cut off angle</font> </td> 
            <td> <input type="range" id="cutOffAngle" min="1" max="180" value="0"/></td> </tr>
</table>
</form>
</div>

<canvas id="glow-canvas" style="border: none;"></canvas>

<a id="ref-link" href="https://stackoverflow.com/questions/45783444/glsl-spotlight-projection-volume/45796941#45796941">
<font color= #CCF>GLSL spotlight projection volume</font>
</a>

<script type="text/javascript">

(function loadscene() {

var sliderScale = 100.0
var gl, canvas, vp_size, camera, progDraw, progLightCone, bufTorus = {}, bufQuad = {}, drawFB;

function render(deltaMS) {

    var ambient = document.getElementById( "ambient" ).value / sliderScale;
    var diffuse = document.getElementById( "diffuse" ).value / sliderScale;
    var specular = document.getElementById( "specular" ).value / sliderScale;
    var shininess = document.getElementById( "shininess" ).value;
    var cutOffAngle = document.getElementById( "cutOffAngle" ).value;

    // setup view projection and model
    vp_size = [canvas.width, canvas.height];
    camera.Update( vp_size );
    var prjMat = camera.Perspective();
    var viewMat = camera.Orbit();
    var modelMat = IdentM44();
    modelMat = camera.AutoModelMatrix();
        
    var lightPos = [0.95, 0.95, -1.0];
    var lightDir = [-1.0, -1.0, -3.0];
    var lightCutOffAngleRad = cutOffAngle * Math.PI / 180.0;
    var lightAtt = [0.7, 0.1, 0.5];

    drawFB.Bind( true );    
    gl.enable( gl.DEPTH_TEST );
    gl.clearColor( 0.0, 0.0, 0.0, 1.0 );
    gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );

    ShProg.Use( progDraw );
    ShProg.SetM44( progDraw, "u_projectionMat44", prjMat );
    ShProg.SetM44( progDraw, "u_viewMat44", viewMat );
    ShProg.SetF3( progDraw, "u_light.position", lightPos );
    ShProg.SetF3( progDraw, "u_light.direction", lightDir );
    ShProg.SetF1( progDraw, "u_light.ambient", ambient );
    ShProg.SetF1( progDraw, "u_light.diffuse", diffuse );
    ShProg.SetF1( progDraw, "u_light.specular", specular );
    ShProg.SetF1( progDraw, "u_light.shininess", shininess );
    ShProg.SetF3( progDraw, "u_light.attenuation", lightAtt );
    ShProg.SetF1( progDraw, "u_light.cutOffAngle", lightCutOffAngleRad );
    ShProg.SetM44( progDraw, "u_modelMat44", modelMat );

    bufObj = bufTorus;
    gl.enableVertexAttribArray( progDraw.inPos );
    gl.enableVertexAttribArray( progDraw.inNV );
    gl.enableVertexAttribArray( progDraw.inCol );
    gl.bindBuffer( gl.ARRAY_BUFFER, bufObj.pos );
    gl.vertexAttribPointer( progDraw.inPos, 3, gl.FLOAT, false, 0, 0 );
    gl.bindBuffer( gl.ARRAY_BUFFER, bufObj.nv );
    gl.vertexAttribPointer( progDraw.inNV, 3, gl.FLOAT, false, 0, 0 ); 
    gl.bindBuffer( gl.ARRAY_BUFFER, bufObj.col );
    gl.vertexAttribPointer( progDraw.inCol, 3, gl.FLOAT, false, 0, 0 );
    gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, bufObj.inx );
    gl.drawElements( gl.TRIANGLES, bufObj.inxLen, gl.UNSIGNED_SHORT, 0 );
    gl.disableVertexAttribArray( progDraw.pos );
    gl.disableVertexAttribArray( progDraw.nv );
    gl.disableVertexAttribArray( progDraw.col );

    drawFB.Release( true );
    gl.viewport( 0, 0, canvas.width, canvas.height );
    var texUnitDraw = 2;
    drawFB.BindTexture( texUnitDraw );
    ShProg.Use( progLightCone );
    ShProg.SetI1( progLightCone, "u_colorAttachment0", texUnitDraw );
    ShProg.SetF2( progLightCone, "u_depthRange", [ camera.near, camera.far ] );
    ShProg.SetF2( progLightCone, "u_vp", camera.vp );
    ShProg.SetF1( progLightCone, "u_fov", camera.fov_y * Math.PI / 180.0 );
    ShProg.SetF3( progLightCone, "u_light.position", lightPos );
    ShProg.SetF3( progLightCone, "u_light.direction", lightDir );
    ShProg.SetF3( progLightCone, "u_light.attenuation", lightAtt );
    ShProg.SetF1( progLightCone, "u_light.cutOffAngle", lightCutOffAngleRad );

    gl.enableVertexAttribArray( progLightCone.inPos );
    gl.bindBuffer( gl.ARRAY_BUFFER, bufQuad.pos );
    gl.vertexAttribPointer( progLightCone.inPos, 2, gl.FLOAT, false, 0, 0 );
    gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, bufQuad.inx );
    gl.drawElements( gl.TRIANGLES, bufQuad.inxLen, gl.UNSIGNED_SHORT, 0 );
    gl.disableVertexAttribArray( progLightCone.inPos );

    requestAnimationFrame(render);
}

function initScene() {

    canvas = document.getElementById( "glow-canvas");
    vp_size = [canvas.width, canvas.height];
    gl = canvas.getContext( "experimental-webgl" );
    if ( !gl )
      return;
    
    document.getElementById( "ambient" ).value = 0.25 * sliderScale;
    document.getElementById( "diffuse" ).value = 1.0 * sliderScale;
    document.getElementById( "specular" ).value = 1.0 * sliderScale;
    document.getElementById( "shininess" ).value = 10.0;
    document.getElementById( "cutOffAngle" ).value = 30.0;

    progDraw = ShProg.Create( 
      [ { source : "draw-shader-vs", stage : gl.VERTEX_SHADER },
        { source : "draw-shader-fs", stage : gl.FRAGMENT_SHADER }
      ] );

    progDraw.inPos = ShProg.AttrI( progDraw, "inPos" );
    progDraw.inNV  = ShProg.AttrI( progDraw, "inNV" );
    progDraw.inCol = ShProg.AttrI( progDraw, "inCol" );
    if ( progDraw.progObj == 0 )
        return;

    progLightCone = ShProg.Create( 
      [ { source : "light-cone-shader-vs", stage : gl.VERTEX_SHADER },
        { source : "light-cone-shader-fs", stage : gl.FRAGMENT_SHADER }
      ] );
    progLightCone.inPos = ShProg.AttrI( progDraw, "inPos" );
    if ( progDraw.progObj == 0 )
        return;

    var circum_size = 32, tube_size = 32;
    var rad_circum = 1.5;
    var rad_tube = 0.8;
    var torus_pts = [];
    var torus_nv = [];
    var torus_col = [];
    var torus_inx = [];
    var col = [1, 0.5, 0.0];
    for ( var i_c = 0; i_c < circum_size; ++ i_c ) {
        var center = [
            Math.cos(2 * Math.PI * i_c / circum_size),
            Math.sin(2 * Math.PI * i_c / circum_size) ]
        for ( var i_t = 0; i_t < tube_size; ++ i_t ) {
            var tubeX = Math.cos(2 * Math.PI * i_t / tube_size)
            var tubeY = Math.sin(2 * Math.PI * i_t / tube_size)
            var pt = [
                center[0] * ( rad_circum + tubeX * rad_tube ),
                center[1] * ( rad_circum + tubeX * rad_tube ),
                tubeY * rad_tube ]
            var nv = [ pt[0] - center[0] * rad_tube, pt[1] - center[1] * rad_tube, tubeY * rad_tube ]
            torus_pts.push( pt[0], pt[1], pt[2] );
            torus_nv.push( nv[0], nv[1], nv[2] );
            torus_col.push( col[0], col[1], col[2] );
            var i_cn = (i_c+1) % circum_size
            var i_tn = (i_t+1) % tube_size
            var i_c0 = i_c * tube_size; 
            var i_c1 = i_cn * tube_size; 
            torus_inx.push( i_c0+i_t, i_c0+i_tn, i_c1+i_t, i_c0+i_tn, i_c1+i_t, i_c1+i_tn )
        }
    }
    bufTorus.pos = gl.createBuffer();
    gl.bindBuffer( gl.ARRAY_BUFFER, bufTorus.pos );
    gl.bufferData( gl.ARRAY_BUFFER, new Float32Array( torus_pts ), gl.STATIC_DRAW );
    bufTorus.nv = gl.createBuffer();
    gl.bindBuffer( gl.ARRAY_BUFFER, bufTorus.nv );
    gl.bufferData( gl.ARRAY_BUFFER, new Float32Array( torus_nv ), gl.STATIC_DRAW );
    bufTorus.col = gl.createBuffer();
    gl.bindBuffer( gl.ARRAY_BUFFER, bufTorus.col );
    gl.bufferData( gl.ARRAY_BUFFER, new Float32Array( torus_col ), gl.STATIC_DRAW );
    bufTorus.inx = gl.createBuffer();
    gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, bufTorus.inx );
    gl.bufferData( gl.ELEMENT_ARRAY_BUFFER, new Uint16Array( torus_inx ), gl.STATIC_DRAW );
    bufTorus.inxLen = torus_inx.length;

    bufQuad.pos = gl.createBuffer();
    gl.bindBuffer( gl.ARRAY_BUFFER, bufQuad.pos );
    gl.bufferData( gl.ARRAY_BUFFER, new Float32Array( [ -1.0, -1.0, 1.0, -1.0, 1.0, 1.0, -1.0, 1.0 ] ), gl.STATIC_DRAW );
    bufQuad.inx = gl.createBuffer();
    gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, bufQuad.inx );
    gl.bufferData( gl.ELEMENT_ARRAY_BUFFER, new Uint16Array( [ 0, 1, 2, 0, 2, 3 ] ), gl.STATIC_DRAW );
    bufQuad.inxLen = 6;

    camera = new Camera( [0, 4, 0.0], [0, 0, 0], [0, 0, 1], 90, vp_size, 0.5, 100 );

    window.onresize = resize;
    resize();
    requestAnimationFrame(render);
}

function resize() {
    //vp_size = [gl.drawingBufferWidth, gl.drawingBufferHeight];
    vp_size = [window.innerWidth, window.innerHeight];
    //vp_size = [256, 256]
    canvas.width = vp_size[0];
    canvas.height = vp_size[1];

    var fbsize = Math.max(vp_size[0], vp_size[1]);
    fbsize = 1 << 31 - Math.clz32(fbsize); // nearest power of 2

    var fb_rect = [fbsize, fbsize];
    drawFB = FrameBuffer.Create( fb_rect );
}

function Fract( val ) { 
    return val - Math.trunc( val );
}
function CalcAng( deltaMS, intervall ) {
    return Fract( deltaMS / (1000*intervall) ) * 2.0 * Math.PI;
}
function CalcMove( deltaMS, intervall, range ) {
    var pos = self.Fract( deltaMS / (1000*intervall) ) * 2.0
    var pos = pos < 1.0 ? pos : (2.0-pos)
    return range[0] + (range[1] - range[0]) * pos;
}    

function IdentM44() { return [1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1]; }

function RotateAxis(matA, angRad, axis) {
    var aMap = [ [1, 2], [2, 0], [0, 1] ];
    var a0 = aMap[axis][0], a1 = aMap[axis][1]; 
    var sinAng = Math.sin(angRad), cosAng = Math.cos(angRad);
    var matB = matA.slice(0);
    for ( var i = 0; i < 3; ++ i ) {
        matB[a0*4+i] = matA[a0*4+i] * cosAng + matA[a1*4+i] * sinAng;
        matB[a1*4+i] = matA[a0*4+i] * -sinAng + matA[a1*4+i] * cosAng;
    }
    return matB;
}

function Rotate(matA, angRad, axis) {
    var s = Math.sin(angRad), c = Math.cos(angRad);
    var x = axis[0], y = axis[1], z = axis[2]; 
    matB = [
        x*x*(1-c)+c,   x*y*(1-c)-z*s, x*z*(1-c)+y*s, 0,
        y*x*(1-c)+z*s, y*y*(1-c)+c,   y*z*(1-c)-x*s, 0,
        z*x*(1-c)-y*s, z*y*(1-c)+x*s, z*z*(1-c)+c,   0,
        0,             0,             0,             1 ];
    return Multiply(matA, matB);
}    

function Multiply(matA, matB) {
    matC = IdentM44();
    for (var i0=0; i0<4; ++i0 )
        for (var i1=0; i1<4; ++i1 )
            matC[i0*4+i1] = matB[i0*4+0] * matA[0*4+i1] + matB[i0*4+1] * matA[1*4+i1] + matB[i0*4+2] * matA[2*4+i1] + matB[i0*4+3] * matA[3*4+i1]  
    return matC;
}

function Cross( a, b ) { return [ a[1] * b[2] - a[2] * b[1], a[2] * b[0] - a[0] * b[2], a[0] * b[1] - a[1] * b[0], 0.0 ]; }
function Dot( a, b ) { return a[0]*b[0] + a[1]*b[1] + a[2]*b[2]; }
function Normalize( v ) {
    var len = Math.sqrt( v[0] * v[0] + v[1] * v[1] + v[2] * v[2] );
    return [ v[0] / len, v[1] / len, v[2] / len ];
}

Camera = function( pos, target, up, fov_y, vp, near, far ) {
this.Time = function() { return Date.now(); }
this.pos = pos;
this.target = target;
this.up = up;
this.fov_y = fov_y;
this.vp = vp;
this.near = near;
this.far = far;
this.orbit_mat = this.current_orbit_mat = this.model_mat = this.current_model_mat = IdentM44();
this.mouse_drag = this.auto_spin = false;
this.auto_rotate = true;
this.mouse_start = [0, 0];
this.mouse_drag_axis = [0, 0, 0];
this.mouse_drag_angle = 0;
this.mouse_drag_time = 0;
this.drag_start_T = this.rotate_start_T = this.Time();
this.Ortho = function() {
    var fn = this.far + this.near;
    var f_n = this.far - this.near;
    var w = this.vp[0];
    var h = this.vp[1];
    return [
        2/w, 0,   0,       0,
        0,   2/h, 0,       0,
        0,   0,   -2/f_n,  0,
        0,   0,   -fn/f_n, 1 ];
};  
this.Perspective = function() {
    var n = this.near;
    var f = this.far;
    var fn = f + n;
    var f_n = f - n;
    var r = this.vp[0] / this.vp[1];
    var t = 1 / Math.tan( Math.PI * this.fov_y / 360 );
    return [
        t/r, 0, 0,          0,
        0,   t, 0,          0,
        0,   0, -fn/f_n,   -1,
        0,   0, -2*f*n/f_n, 0 ];
}; 
this.LookAt = function() {
    var mz = Normalize( [ this.pos[0]-this.target[0], this.pos[1]-this.target[1], this.pos[2]-this.target[2] ] );
    var mx = Normalize( Cross( this.up, mz ) );
    var my = Normalize( Cross( mz, mx ) );
    var tx = Dot( mx, this.pos );
    var ty = Dot( my, this.pos );
    var tz = Dot( [-mz[0], -mz[1], -mz[2]], this.pos ); 
    return [mx[0], my[0], mz[0], 0, mx[1], my[1], mz[1], 0, mx[2], my[2], mz[2], 0, tx, ty, tz, 1]; 
};
this.Orbit = function() {
    return Multiply(this.LookAt(), this.OrbitMatrix());
}; 
this.OrbitMatrix = function() {
    return (this.mouse_drag || (this.auto_rotate && this.auto_spin)) ? Multiply(this.current_orbit_mat, this.orbit_mat) : this.orbit_mat;
};
this.AutoModelMatrix = function() {
    return this.auto_rotate ? Multiply(this.current_model_mat, this.model_mat) : this.model_mat;
};
this.Update = function(vp_size) {
    if (vp_size)
        this.vp = vp_size;
    var current_T = this.Time();
    this.current_model_mat = IdentM44()
    if (this.mouse_drag) {
        this.current_orbit_mat = Rotate(IdentM44(), this.mouse_drag_angle, this.mouse_drag_axis);
    } else if (this.auto_rotate) {
        if (this.auto_spin ) {
            if (this.mouse_drag_time > 0 ) {
                var angle = this.mouse_drag_angle * (current_T - this.rotate_start_T) / this.mouse_drag_time;
                this.current_orbit_mat = Rotate(IdentM44(), angle, this.mouse_drag_axis);
            }
        } else {
            var auto_angle_x = Fract( (current_T - this.rotate_start_T) / 13000.0 ) * 2.0 * Math.PI;
            var auto_angle_y = Fract( (current_T - this.rotate_start_T) / 17000.0 ) * 2.0 * Math.PI;
            this.current_model_mat = RotateAxis( this.current_model_mat, auto_angle_x, 0 );
            this.current_model_mat = RotateAxis( this.current_model_mat, auto_angle_y, 1 );
        }
    }
};
this.ChangeMotionMode = function(drag, spin, auto ) {
    var new_drag = drag;
    var new_auto = new_drag ? false : auto;
    var new_spin = new_auto ? spin : false;
    change = this.mouse_drag != new_drag || this.auto_rotate != new_auto || this.auto_spin != new_spin; 
    if (!change)
        return;
    if (new_drag && !this.mouse_drag) {
        this.drag_start_T = this.Time();
        this.mouse_drag_angle = 0.0;
        this.mouse_drag_time = 0;
    }
    if (new_auto && !this.auto_rotate)
        this.rotate_start_T = this.Time();
    this.mouse_drag = new_drag; 
    this.auto_rotate = new_auto;  
    this.auto_spin = new_spin;
    this.orbit_mat = Multiply(this.current_orbit_mat, this.orbit_mat);
    this.current_orbit_mat = IdentM44();
    this.model_mat = Multiply(this.current_model_mat, this.model_mat);
    this.current_model_mat = IdentM44();
};
this.OnMouseDown = function( event ) {
    var rect = gl.canvas.getBoundingClientRect();
    if ( event.clientX < rect.left || event.clientX > rect.right ) return;
    if ( event.clientY < rect.top || event.clientY > rect.bottom ) return;
    if (event.button == 0) { // left button
        this.mouse_start = [event.clientX, event.clientY]; 
        this.ChangeMotionMode( true, false, false );
    }
};
this.OnMouseUp = function( event ) {
    if (event.button == 0) { // left button
        this.ChangeMotionMode( false, true, true );
    } else if (event.button == 1) {// middle button
        this.ChangeMotionMode( false, false, !this.auto_rotate );
    }
};
this.OnMouseMove = function( event ) {
    var dx = (event.clientX-this.mouse_start[0]) / this.vp[0];
    var dy = (event.clientY-this.mouse_start[1]) / this.vp[1];
    var len = Math.sqrt(dx*dx + dy*dy);
    if (this.mouse_drag && len > 0) {
        this.mouse_drag_angle = Math.PI*len;
        this.mouse_drag_axis = [dy/len, 0, -dx/len];
        this.mouse_drag_time = this.Time() - this.drag_start_T;
    }
};

this.domElement = document;
var cam = this;
//this.domElement.addEventListener( 'contextmenu', function(e) { event.preventDefault(); }, false );
this.domElement.addEventListener( 'mousedown', function(e) { cam.OnMouseDown(e) }, false );
this.domElement.addEventListener( 'mouseup', function(e) { cam.OnMouseUp(e) }, false );
this.domElement.addEventListener( 'mousemove', function(e) { cam.OnMouseMove(e) }, false );
//this.domElement.addEventListener( 'mousewheel', hid_events.onMouseWheel, false );
//this.domElement.addEventListener( 'DOMMouseScroll', hid_events.onMouseWheel, false ); // firefox
} 

var FrameBuffer = {};
FrameBuffer.Create = function( vp, texturePlan ) {
    var texPlan = texturePlan ? new Uint8Array( texturePlan ) : null;
    var fb = gl.createFramebuffer();
    var fbsize = Math.max(vp[0], vp[1]);
    fbsize = 1 << 31 - Math.clz32(fbsize); // nearest power of 2
    fb.width = fbsize;
    fb.height = fbsize;
    gl.bindFramebuffer( gl.FRAMEBUFFER, fb );
    fb.color0_texture = gl.createTexture();
    gl.bindTexture( gl.TEXTURE_2D, fb.color0_texture );
    gl.texImage2D( gl.TEXTURE_2D, 0, gl.RGBA, fb.width, fb.height, 0, gl.RGBA, gl.UNSIGNED_BYTE, texPlan );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST );
    fb.renderbuffer = gl.createRenderbuffer();
    gl.bindRenderbuffer( gl.RENDERBUFFER, fb.renderbuffer );
    gl.renderbufferStorage( gl.RENDERBUFFER, gl.DEPTH_COMPONENT16, fb.width, fb.height );
    gl.framebufferTexture2D( gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, fb.color0_texture, 0 );
    gl.framebufferRenderbuffer( gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.RENDERBUFFER, fb.renderbuffer );
    gl.bindTexture( gl.TEXTURE_2D, null );
    gl.bindRenderbuffer( gl.RENDERBUFFER, null );
    gl.bindFramebuffer( gl.FRAMEBUFFER, null );

    fb.Bind = function( clear ) {
        gl.bindFramebuffer( gl.FRAMEBUFFER, this );
        if ( clear ) {
            gl.viewport( 0, 0, this.width, this.height );
            gl.clearColor( 0.0, 0.0, 0.0, 1.0 );
            gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );
        }
    };

    fb.Release = function( clear ) {
        gl.bindFramebuffer( gl.FRAMEBUFFER, null );
        if ( clear ) {
            gl.clearColor( 0.0, 0.0, 0.0, 1.0 );
            gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );
        }
    };

    fb.BindTexture = function( textureUnit ) {
        gl.activeTexture( gl.TEXTURE0 + textureUnit );
        gl.bindTexture( gl.TEXTURE_2D, this.color0_texture );
    };

    return fb;
}

var ShProg = {
Create: function (shaderList) {
    var shaderObjs = [];
    for (var i_sh = 0; i_sh < shaderList.length; ++i_sh) {
        var shderObj = this.Compile(shaderList[i_sh].source, shaderList[i_sh].stage);
        if (shderObj) shaderObjs.push(shderObj);
    }
    var prog = {}
    prog.progObj = this.Link(shaderObjs)
    if (prog.progObj) {
        prog.attrInx = {};
        var noOfAttributes = gl.getProgramParameter(prog.progObj, gl.ACTIVE_ATTRIBUTES);
        for (var i_n = 0; i_n < noOfAttributes; ++i_n) {
            var name = gl.getActiveAttrib(prog.progObj, i_n).name;
            prog.attrInx[name] = gl.getAttribLocation(prog.progObj, name);
        }
        prog.uniLoc = {};
        var noOfUniforms = gl.getProgramParameter(prog.progObj, gl.ACTIVE_UNIFORMS);
        for (var i_n = 0; i_n < noOfUniforms; ++i_n) {
            var name = gl.getActiveUniform(prog.progObj, i_n).name;
            prog.uniLoc[name] = gl.getUniformLocation(prog.progObj, name);
        }
    }
    return prog;
},
AttrI: function (prog, name) { return prog.attrInx[name]; },
UniformL: function (prog, name) { return prog.uniLoc[name]; },
Use: function (prog) { gl.useProgram(prog.progObj); },
SetI1: function (prog, name, val) { if (prog.uniLoc[name]) gl.uniform1i(prog.uniLoc[name], val); },
SetF1: function (prog, name, val) { if (prog.uniLoc[name]) gl.uniform1f(prog.uniLoc[name], val); },
SetF2: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform2fv(prog.uniLoc[name], arr); },
SetF3: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform3fv(prog.uniLoc[name], arr); },
SetF4: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform4fv(prog.uniLoc[name], arr); },
SetM33: function (prog, name, mat) { if (prog.uniLoc[name]) gl.uniformMatrix3fv(prog.uniLoc[name], false, mat); },
SetM44: function (prog, name, mat) { if (prog.uniLoc[name]) gl.uniformMatrix4fv(prog.uniLoc[name], false, mat); },
Compile: function (source, shaderStage) {
    var shaderScript = document.getElementById(source);
    if (shaderScript)
        source = shaderScript.text;
    var shaderObj = gl.createShader(shaderStage);
    gl.shaderSource(shaderObj, source);
    gl.compileShader(shaderObj);
    var status = gl.getShaderParameter(shaderObj, gl.COMPILE_STATUS);
    if (!status) alert(gl.getShaderInfoLog(shaderObj));
    return status ? shaderObj : null;
},
Link: function (shaderObjs) {
    var prog = gl.createProgram();
    for (var i_sh = 0; i_sh < shaderObjs.length; ++i_sh)
        gl.attachShader(prog, shaderObjs[i_sh]);
    gl.linkProgram(prog);
    status = gl.getProgramParameter(prog, gl.LINK_STATUS);
    if ( !status ) alert(gl.getProgramInfoLog(prog));
    return status ? prog : null;
} };
        
initScene();

})();

</script>

</body>
